The mount points are only defined in /etc/fstab and are dynamically shown in /etc/mtab (typically emptied during boot) and /proc/mounts (a virtual file, populated by a running kernel). If you have lost /etc/fstab in the OS HDD failure then the information is lost. You may be able to work out where each remaining file system was mounted by listing it top level directories, for example /var would have something like:
cache
db
empty
games
lib
lock
log
man
named
opt
run
spool
state
tmp
www
yp
The
Filesystem Hierarchy Standard (FHS) would help in such detective work.
